Treatment of hydrocarbon oils



countered 'in handling refined products.

fore, corrosion occurring in the transportation.

Patented Jan. 9, 1945 TREATMENT OF HYDROCARBONOILS Walter A. Schulze,Bartlesville, Okla, assignor to Phillips Petroleum Company, acorporation of Delaware No Drawing.

10 Claims.

This invention relates to the prevention, inhibition and restriction ofthe corrosion of metals.

More specifically this invention relates to the restriction orprevention of corrosion when such action involves metals subject tocorrosion in contact with refined hydrocarbon fluids and especiallywhenalso in contact with water, aqueous solutions or other aqueous material.

In the petroleum industry huge losses are suffered due to the internalcorrosion of ferrous and other metal facilities for the handling,transpor- Application January 2, 1942, SerialNo. 425,479

tation and storage of refined hydrocarbon oils,

liquefied gases and natural gas. Especially is this true of pipelinesused to transport said fluids andthe tanks in which the fluids arestored;

therate and extent of corrosion associated with essentially neutralorwith alkaline solutions de-- pend on the occurrence and the rate ofReaction 2. Speller reportsfinding that in naturalwaters the rate ofcorrosion was almost directly proportional to the oxygen concentrationup to about 6 cubic centimeters of oxygen per liter of water.

I have noted that the corrosion of metals in contact with refinedhydrocarbon fluids and water or moderately alkaline-solutions isdependent on the presence of free oxygen in the aqueous phase and/or thehydrocarbon fluid. In the ease of a large quantity of a hydrocarbonliquid in contact Serious corrosion problems also arise in the refiningof oils and in the manufacturing processes involved, but such corrosionis generally beyond the intended scope of this invention.

Hydrocarbon fluids are not usually corrosive to metals in the absence ofan aqueous phase and of free oxygen except in the case of fiuidscontalning corrosive materials such as hydrogen sulfide and the like.Also only in unusual circumstances are stronglyacidic aqueous solutionsen- Thereand storage of said refined products is dependent primarily onthe presence of a practically neutral or an alkaline aqueous phase andfree oxygen. In the presence of even'a trace of aqueous materialcorrosion of the metal occurs according I to the reactions generallyaccepted for the corrosion of metals in water and illustrated below.

The extent of the corrosion. of metals in contact with an aqueous phasedepends on the presence of oxygen gas in the case of neutral or alkalinesolutions oron the evolution of hydrogen in the case of acid solutions.Thus, for metals in contact with a non-acidic aqueous'phase the rate ofcorrosion is almost directly proportional to the concentration of freeoxygen if other factors are constant.

The chemical reactions assumed to predominate during corrosion are thefollowing as listed on page 14 of Corrosion-Causes and Prevention," i i2nd ed. (1935) byF. N. Speller:

atoms gas liquid Assuming that in the presence of an aqueous.

phase, Reaction 1 isextremelyirapid regardless and/or deactivating theoxygen concentration of hydrocarbon fluidsand hence reducing or limitofthe pH of the aqueous medium, it follows that 55 with water and a metalsurface, corrosion may be severe because oxygen gas is even moresoluble'in the hydrocarbon than in the aqueous phase and a plentifulsupply of oxygen is assured at the metal surface by transfer from thehydrocarbon liquid. In order to restrict corrosionin such cases, thehydrocarbons might be substantially completely dehydrated and storedinthe absence of water, but such operations are usually not economicallyfeasible. Heretofore no feasible means of substantially reducing theoxygen content of hydrocarbon fluids has been available. l

The removalof oxygen gas from water in order to control corrosion inpiping systems has long been practiced through the useof so-calleddeactivators such as scrap iron. The de-aeration of water has also beenpracticed by heating and evacuation, followed in some cases by achemical treatment with reagents such as a sulfite. Such methods,however, are not successfully adapted to the treatment of hydrocarbonfluids.

It is the principal object ofthis invention to restrict and/or preventthe internal corrosion of metal tanks, pressure vessels and pipelinesused for storing or transporting refined hydrocarbon fluids. i V iAnother object of this invention istoreduce the corrosion of metalcontainer and pipelines for,

refined hydrocarbon fluids by substantiallyreducing the oxygen contentof said fluids.

A further object is to prolong the'service life and decrease themaintenance costs of metal equipment such as tanks, vessels, andpipelines used in. storing and/or transporting refined hydrocarbonfluids by. decreasing the internal corrosion thereof. These and numerousother objects will beapparent from the-following disclosure. i

I have now discovered a process for reducin ing the oxygen content ofany aqueous phase with which said hydrocarbon fluids may be in contact.Thisprocess provides an eflicient means of restricting. the corrosion ofcorrodible metals in contact with said hydrocarbon fluids and theattendant aqueous phase.

Hydrocarbon oils, by reason of their ability to dissolve air and/oroxygen-containing gases, always contain an amount of free oxygen whichmay range from small concentrations of less than toward the hydrocarbonsunder the conditionsemployed but reactive with free} oxygen therein.

Forexample. I may ernnloyhydrogen and/or car bon monoxideinquantities-sufilcient to react withfree oxygen accordingto the followingequations:

with the hydrocarbon, the mixture being subjected to reaction pressurefor a period of time sufficient to react at least a substantialproportion of the oxygen therein. The pressure may then be .released orpreferably maintained throughout the period of storage ortransportation.

For example as gasolineis pumped intoa storage tank or pipeline it maybesubjected in a separate zone to treatment in accordance with the presentinvention on its way to the storage tank or pipeline. Or it may betreated in accordance with the present invention in thestorage tank orpipeline itself, as by introducing the reducing gas by meansof suitableorifices or in other manner designed to efiect intimate and prolongedinter mixture with the entire body of gasoline. In the case of apipeline, the gas may be introduced bet fore, or at the point of,.theintroduction of the Other reactions: whioh-mawinvolve the reducing Igases are thereduc'tion of" iron and other metal oxides which maybepresent as'a result of previous corros on; but reactions- 3andr4'predominate" in most'cas'es;

These reactions" are relatively slow at'atmos-- pheric temperatures-andpressuresrbut under the: conditio'nsemnl'oyed 'in rhyprocess roceedfaster than the corro ionReacti i-rs 1 and 2 listed above."

Th s is due to the remarkable acceleratin effect" of'increased'pressureon reactions of the reducing: gases w ich comnensatesinpart'fo'rthelowitemperatures employed Further: and: probably veryimportant to itheo'peration' of the process; the' me al oxides alwayspresent on co'rrodible'metal surfaces are powerful catak'sts for thereaction of h d o en an carb n monoxide with. oxy en. and thusaccountlfo'r a greatincrease'in reaction rates. H

In accordance with my invention; hydrocarbon, w c is u ual in liou dor'liquefi'ed condi ion. whic is generally of petroleum ori n and whichmav b a inha icsuch as 'oaraflinic or olefin c; aro'm atic; na'ohthenicor ofmixed-type and which contai s ox gen d ssolved the ein. withor'without a seoarate oxygen-conta ning gaseous phase, is comming edwith a reducing as, preferably hy r en and/ or car on mon xide;in-"amount' si fiicient t react withall, the xygen resent and"preferably in great excess. The mixture is sub-- jeoted atordinarilv encunteredtemperatures to elevated. pressure sufiicintly high to bringabout combina ion of the reducing gas with a substantial ortion of, andpreferably at least of. up

to substant al y all of. the" oxygen present. The

= ous. phasewillbe present. However itrmay be. desired in some instancesto employ such. an.ex-. cess of the reducing gas over theoreticalrequired; to combine withthe free oxygen. present. that. such aseparategaseous phase is present and.

and such reaction conditions as to reduce the:

oxygen content of such gaseous-phase tobelow about 0;002%, andbetterstill-to below: about hydrocarbon to the pipeline and at suitableintervals thereafter as required.

The minimumpressure required will'varyfto some'exte'nt inversely withthe temperature, but

in general should be at least about 5 atmospheres" absolute andpreferably at least about 10 atmospheres. The temperature maybe thatnormally obtaining under typical atmospheric conditions andwill usuallylie between about -30F. and about 200 F. It will be understoodthat'while the temperature of. the air may not rise ashigh as this, theaction of the sunis raysmay. raise thetemperaturewithin exposed storagetanks or .p p

linessomewhat above the temperature of theair.

In general, however, no extraneous heatv is delilclcrate-1yv applied.to. promote the, reaction.

A. separate gaseous phase in contact, with. the.

hydrocarbon liquidunder treatment. may or. may

not be.present,as,desired.- Frequently, asdnpipelines or in the case ofliquefiednormally gaseous,

hydrocarbons which exhibit high. solvent.v action onthe reducing gasvusedf no such separate; gasemaintained during storage.

aqueous phase in. contact hydrocarbon.

While the invention is generally applied to hydrocarbons'in liquid orliquefied form,-itmay be applied to gaseous hydrocarbons containingoxygen.

In accordance with my: invention the dissolved oxygencontent of" thehydrocarbon liquid is reacted and therebyiremoved. Iimay'usersuchsan.

amount'zof hydrogen. or" CO andsucnrea'ctiorrconditions'asfto'reduceithe oxygen contentto le'ss: than about 0.2% byvolume (2 cc. of oxygen per liter) and preferably to'less than about0.1%"1 y ed in accordance withthe. presentinvention, or

where an oxygen-containing gaseous phase is in contact with thehydrocarbon liquid, it is pre-' ferred to use such an amount of thereducing gas Where a corrosion.

hydrocarbon gases.

0.001%; er oxygen by :volu es er: nai aseaus phase; i

My process ise conomicallyapplied as anaddi tional step in the storageand transportation of hydrocarbon fluids since such operations mayconveniently be carried out under substantialsuper-atmosphericpressures.Thus; in the stor tainer was liquid full sothat no vapor space ex-u age of gasolines and/or liquefied petroleumgases in spheroid-or other types of pressure tanks, the

addition of hydrogen and/or carbon monoxide gas is an easilyadaptableoperation andpressures may be maintainedwithin'thecontainingvessels at such levels as to favorably influence the reactionbetween the re present in or above the hydrocarbon fluids.

Of even greater importance is the application ducing gas and the oxygenof the process tothe pipeline transportation of portation of gaseous orliquid hydrocarbons including naturahgas, liquefied gases; gasoline,kerosene and the like is ordinarily carried out in a substantiallyclosed system under high transmission pressures and at temperatureswhich are not high, seldom exceeding about 200F. The hydrocarbon fluidwith the associated aqueous phase and free oxygen is constantlyunderpressures ranging. from maximum values of .1000 to refinedhydrocarbonflfiuids. Suchpipeline transsteel container under a pressureof atmospheresand at 'a temperature of 70F. The conisted. After '72hours the container was opened and the gasoline was found to contain 253cc. of oxygen per liter. The reduction in free oxygen content was thus38.5per cent of the original.

oxygen content. This reduction was solely due to reaction of the oxygengas during corrosion l of the steel container according to E quation 2of the above-listed corrosion reactions.

liter was placed in a similarsteel container with a similar proportionof water. Hydrogen gas amounting to 77.6 cc. perliter was added, and

about 1500 {poundsgage at the discharge side of pumping stations tolowervalues ranging down to about .100 to .200 pounds gage at the intakeside-of subsequent pumping units. Under these 1 conditions. of highsuper-atmospheric pressures,

the introduction of a suitable reducing gas at. any

point inthe system initiates the reactions for the removal of. oxygen.or the conversion thereof to substantially inactive .form. MInadditionto the highpressures, the presence-of. metal and metal.

oxides on the internal pipe surfaces promotes the oxygen-removing reaThe amount of reducing gas to be added in the process is determined bytheoxygen content of the hydrocarbon fluid present or-passinga metalsurface to be protected. Ordinarily hydrogen .and/orcarbon monoxide isadded in rather subctionsand therestriction'of stantial excesspftheamount theoretically :re-

quired to react with oxygen according to Equations 3 and 4. The excessnot only favors the reaction but is also a safety factor in caseof-later air-contamination of the fluid. The upper limits for .reducinggas addition may, of course; be

partly determined by the solubilityvof said gases in hydrocarbonliquids, although this factor does not enter in thecase of 1 compressedpetroleum 1 However suchanexcess of the gas may be introduced as to forma separate phase thereof. Otherconsiderations such as economic-factorsor the effect of the added gas on I gas compositionsmayestablishoperating limits. The reducinggasmay beadded all at onepoint or additions may be made intermittently during 1 a storageor'transportationperiodito maintain a t concentration of l desired more1 or less constan active reducing material.-

The following examples will provide specific data and illustrativeconditions regarding the operation of the process, but neither the exam:ples nor the foregoing theoretical considerations are to be construed aslimiting the scope of the invention... Many additional applications willbe evidentin addition to those recorded herein.

Example 1 A blend of cracked and straightrun gasoline was sampled and"upon testingfound to contain the pressure and temperature of the liquidfull container were adjusted to 10 atmospheres and 70 Frrespectively.The 2H21O2 ratio representing reacting gas volumes was 16:1. After 72hours the container was opened and the oxygen content of the gasolinewas found to be 1..06 cc.

per liter. The reduction inthe original content was thus-78.8 per cent,and in the. presence of added hydrogen the increase in free oxygenremoval was about 100 per cent over that found in the absence ofhydrogen. Tests showedthat this increased disappearance'of oxygen wassolely attributable to chemical reaction with the added hydrogen.Moreover at theuend of the '72 hour period most of the hydrogen stillremained in j'unreacted form and was available for future protection.Furthermore the corrosion of the vessel at the end of this run was lessthan the corrosion described in the preced in the comparative run ingparagraph. i

stored under identical conditions without added hydrogen and in aglass-lined steel container. After 72 hours, there. was substantially node g crease in oxygen content, thus showing that "oxygen. was notconsumed by reac asoline.

Example 2 Two samples of a straight run gasoline were} chosen and thefree oxygen content of each determined. A One sample was placed in asteel con tainer withwater but Without added hydrogen;

the second wasplaced in an identical container f underidenticalconditions except that sufiiicient hydrogen gas was added toproduce a2H2:Oz

ratio of 16.5:1. The containers were liquid full andthe pressures were200 pounds per square inch gage at 77 F. for the first and at 80" F. forthe second. Room temperatures were used, which varied from F.to 80 F.during 24 hours, the

temperatureaveraging close to F. After 72 hours storage. the containersWere opened and the [oxygen content of each gasoline sample wasdetermined with results tabulated below.

Final Per cent Added content 2 I content Residual '09 in state igasoline A dded z 1 content 2s 4. 0e, 3. 23 3s. 9 0. e7 4. 11 1. 0s 04.s

All figures except per cent in ccJliter.

Againthe extent offree oxygen removal was: almostlOQ per cent greater inthe case of the 4.11m 10f oxygen'ape'r liter: .T'his'blendtogethen "withenough water tovassure an aqueous phase 1 um-dissolved in the gasolinewasthen placed in a 15 l A second portion of the same type gasoline withi an original free oxygen contentof 4.98 cc. per

A thirdportion of thesame type gasoline was tion with the reduction derit impracticable.

markedly diiferent from such a process because I addxpreviously formedgaseous hydrogen as such samplet'containing addedwhydrogen than: in thel caseofisamplel where oxygen removal'was associated only with corrosionof the container. Moreover this removal of oxygen was attributablechiefly to reaction with: the hydrogen and corrosion of the vessel wasmaterially less even in sho time of the test. I

Example 3 The gasoline of Example 2 was used in comparative tests underconditions identical with Example 2 except that carbon monoxide was usedinstead of hydrogen. 14: 1 the reduction in free oxygen content was 58per cent compared to 32 per cent in thecontainer to which no reducinggas'was added. As before this reduction in free oxygen content wasattributable to reaction with the carbon monoxide and was accompanied byreduced corrosion.

These examples indicate the extent to which corrosion of the corrodiblemetal containers was restricted whenhydrogen and carbon monoxide wereadded to reduce the oxygen content of the hydro-carbon liquid.

Reducing gases especially suitable for the process are hydrogen andcarbon monoxideor mixtures thereof with each other or with other inertnonoxidizing gases and preferably substantially free of oxygen and ofany components not sube stantially inert toward the hydrocarbon fluidsand/or the metal surfaces. It will be obvious that it is highlydesirable to avoid the introduction of oxygen or gases containing it orother oxidiz ing; impurities when the purpose of the process isto'reducecorrosion andthefreeoxygen con-' tent of the materials present.

The reducing gaseswhich are useful are sub- With a 200:02 ratio of'stantially pure hydrogen, substantially pure carbon monoxide,substantially pure mixtures of hy drogen with carbon monoxide. andsimilar gases free from hydrogen sulfide. The ga used should bevfreefrom oxygeinhydrogen sulfide or other reactive or harmful constituents.selected from the group consisting of substan tially pure carbonmonoxide and hydrogen is highly preferred. Since the componentsof suchgases or mixtures are substantially non-conden- Use of a gas sible underordinary conditions they are easily separable. from hydrocarbonliquidsof the. nature of gasoline when theirfunction is completed. It isusually desirable for economic reasons to use gaseswith relatively largeconcentrations of the active reducing components since the volumerequired is calculated on the basis of the active When flue gases orcombustion. gases are available free of. oxygen they may be.

components.

utilized for the carbon monoxide content, and

to use.v a

.Iam aware that it has-beenproposed (II. S. 2,029,748) to generatenascent hydrogen by the action of an addedelectrolyte and. metal in the7 water and carbon dioxide may be removed prior Y bon fluids in a closedsystem under at least about bottompf a bodyof gasoline stored .in aniron storage tank, for the purpose of preventing gum and color-formationin the gasoline. Such .a

process has notattained any commercial useful;

ness, so far as I am aware, apparently because the complications andexpense incident thereto ren- The present invention is directly to thehydrocarbon instead of going through the complications. incident. togeneration of nascent hydrogen in situ. In my pro-cess noelectrolyte isneeded which itself would cause aseaese.

' corrosion of; theiiron. and; other-undesirable; side.-

reactions. Moreover it has not been proposed-g sofar as I. am aware,- tomaintain-a mixture of gasoline and molecular'hydrogen under sumcient;pressure to cause chemical reaction between the hydrogen and dissolvedoxygen. At most previously proposed process involves merely flushing; ofthe gasoline with molecular hydrogen formed from the nascent'hydrogen,at substantiallyata;

mospheric pressure, and whollylfails to teach the bringing about of achemical'reaction between thehydrogen and any dissolved oxygen.Atmospheric pressure is insuflicent to bring about this reaction.Moreover there is no teaching of. any direct analogy between themechanism of gum-forma tion and the mechanism of corrosion of thecontainer. In addition my process is readily adapted,

to transportationof hydrocarbons as in a pipeline. In pipelinetransportation the generation of nascent hydrogen would be whollyimpractica, ble and the maintenance above the hydrocarbon liquid of ahydrogen atmosphere resulting therefrom would likewise be impossible.Even in the case of pipeline transportation of gaseous or vaporhydrocarbons, maintenance of a separate phase of hydrogen would beimpossible. Moreover the pressures used in pipeline transportation wouldnecessarily far exceed anything contemplated. in

the'prior process under discussion. Another point of distinction is thatin my process the reducing f gas may be introduced to or commingled"with the hydrocarbon either in a separate treating zone as th'ehydrocarbcns'is fedinto the. storage tank or pipeline" or may be, pumpedinto the hydrocarbon' in the storag'e'tank after the hydro- "carbon hasbeen introduced into the storage tank or may. be'pumpedinto the storagetank or pipeline simultaneously with the hydrocarbon either separatelytherefrom or with the hydrocarbon;

The corrodible metals contemplated by the present invention usuallycomprise either iron or" copper.

Thepresent invention is applicable whether or not'water-or other aqueousmaterial be present in contact with the hydrocarbon andwhether or a notsuchaqueous material be in solution in the hydrocarbon or present as aseparate aqueous phase. .Iclaim: 1

l. The process for reducing the corrosiveness of hydrocarbon fluidscontaining oxygen upon metals which comprises commingling with areducing gas in sufiicient quantity to react with a substantial portionof said oxygen and subjecting the mixture to a pressure of at leastabout 5 atm'ospheres at a temperature of from aboi1t'-30" to about 200F.to efiect said'reaction.

2. A process for the restriction of the corrosion of corrodible metalsin contact 'with hydrocarbon fluids associated with free oxygen and anaqueous phase which comprises addin to said hydrdcar- 5 atmospherespressure andatordinary temperatures'carbon monoxide gas substantially inex-' cess of theoretical quantities required for reac tion with the freeoxygen'p'resent said system. 3. 'A process for the restriction of thecorrosion at ordinary temperatures of corrodible metals in contact withrefined hydrocarbon fluids associated with free oxygenand an-aqueousmedium which comprises adding-tosaid hydrocarbon fluids in a,

closed system under at least'about 5 atmospheres pressure an efiectiveamount of hydrogen gas in molecular form whereby the Oxygen content ofsaid system is substantially reduced.

4. A process for the restriction of the corrosion at ordinarytemperatures ofoorrodible metals in contact with refined hydrocarbonfluids associated with free oxygen and an aqueous medium which comprisesadding to said hydrocarbon fluids in a closedsystem under at least aboutatmospheres pressure an effective amount of carbon monoxide whereby theoxygen content of said system is substantially reduced. r n

5. The method of preventing corrosion of corrodible metal containersused for the storage of 1 hydrocarbon fluids containing oxygen whichcom-i with said oxygen of areducing gas selected from i the groupconsisting of hydrogen and carbon monoxide and transporting theresulting mixture in said pipeline at atmospheric temperature and undera pressure of at least about 5 atmospheres.

'l. The method of preventing corrosion of corrodible pipelines used forthe transportation of theoretical required to combine with said oxygenof a reducing as selected from the group consisting of hydrogen andcarbon monoxide, transporting the resulting mixtur in said pipeline atatmospheric temperature and under a pressure of A at least about 5atmospheres, and at intervals in said pipeline introducing additionalportions of said gas. i

8. The process for reducing the corrosiveness of hydrocarbon liquidscontaining oxygen upon metals which comprises commingling said liquidswith molecular hydrogen in excess of the amount theoretically needed toreact with the oxygen in the hydrocarbon liquids at a pressure ofsubstangage and a temtially 200 pounds per square inch perature ofbetween and F.

9. The process for reducing the corrosiveness of hydrocarbon liquidscontaining oxygen upon metals which comprises commingling said liquidswith molecular hydrogen in excess of the amount theoretically needed toreact with the oxygen in the hydrocarbon liquid at a pressure of atleast 5 atmospheres absolute and a temperature or between -30 F. and 200F.

r 10. The process for reducing the corrosiveness "of hydrocarbon liquidscontaining oxygen upon metals which comprises commingling said liquidswith a reducin gas of molecular form selected from the group consistingof hydrogen and carbon monoxide in excess of the amount theoretically 4needed to'react with the oxygen in the hydrocarbon liquid at a pressureof at least 5 atmoshydrocarbon liquid containing oxygen which fcomprises introducing into said liquid at the point where it enters saidpipelinean excess over pheres absolute and a temperature of between -30F. and 200 F. r i

WALTER A. SCHULZE.

